Know what you are feeding
When John Jaeger, assistant professor of beef cattle science at Kansas State University (KSU), began receiving inquires from beef producers asking whether or not feeding wet distillers' grains (WDGs) to replacement heifers influenced reproduction, he and his colleagues decided the question merited a comprehensive study.
“We were getting a lot of calls from producers who were seeing poor conception rates when WDGs were used as a protein supplement,” recalls Jaeger.
The study compared the performance of heifers fed a typical Kansas drylot replacement ration with one that replaced the conventional protein supplement with WDGs.
“Our non-WDGs control was 85% ground sorghum hay, 9.5% ground milo as a protein source, and 7% soybean meal as a protein supplement. The remaining percentage consisted of vitamins, minerals, and salt,” notes Jaeger.
The ration that included WDGs consisted of 65% ground sorghum hay, 7.9% ground milo, and 25.7% WDGs. Cattle fed this ration received the same vitamin, mineral, and salt supplements as the ones fed the non-WDGs diet.
Before the study began, the 172 pre-conditioned, weaned heifers under 1 year received 60 days of growers followed by two weeks of the diet they would receive during the study. “This allowed the animals to adjust to the study diet, which reduced the variables in the study and improved accuracy,” says Jaeger.
Several factors considered
In building the study parameters, the researchers didn't just restrict their investigation to conception rates. Instead, they felt it was important to monitor weight gain during and after the study. They also recorded when each of the heifers reached puberty.
In order to accomplish this, each animal's weight and body score were recorded every 28 days over the 94-day life of the study. Blood samples were also collected for analysis of progesterone levels to determine which heifers were pubertal.
At the end of the study, all heifers were turned on to grass. Half of each group remained for 23 days and were then synchronized by artificial insemination and bred. The remaining animals were bred under identical conditions after 51 days.
Protein intake is the key
While the researchers did not detect any negligible difference between the conception rates of the cattle fed WDGs and those that were not, Jaeger believes other data pointed to a possible reason why producers he spoke with might have experienced conception issues.
“During the feeding period, the average daily gain was less for those fed WDGs,” he says. “The difference was significant – running from .4 to 1 pound a day.”
He says, on average, heifers receiving WDGs reached puberty later than the control group.
To Jaeger and his associates, this indicated the WDGs group was not receiving the level of protein for optimal development. “The fact that all animals were pastured for a period of time afterward allowed the WDGs group to catch up,” he says. “It might mean a small modification to your heifers' diets, but it is definitely doable.”